As a developing device adapted in an image forming apparatus using an electrophotgraphy process, such as a copying machine, a printer, and a facsimile machine, a developing device of a noncontact method, in which the development is performed without contacting a developer carrying body with an image carrying body, has come to receive attention. Suggested therein are methods using a powder cloud method, a jumping method, and a method using an electric field curtain (traveling-wave electric field).
The means to generate the electric field curtain is disclosed in Japanese Unexamined Patent Publication No. 9-68864/1997 (Tokukaihei 9-68864, published on Mar. 11, 1997), for example. This means is arranged so as to include a supporting substrate made of metal or resin, an insulation layer layered on the supporting substrate, and plural sets of three electrodes for generating an electric field curtain effect which are sequentially buried in the insulation layer, wherein the developer is conveyed on a surface of a developer conveying member using the traveling-wave electric field that is formed by applying a polyphase voltage to the respective electrodes.
Incidentally, in the developing device using the traveling-wave electric field, wiring patterns are respectively provided outside of the electrodes on the developer conveying member in the width direction of the electrodes orthogonal to the arranging direction of the electrodes (on both sides of the developer conveying member in a width direction orthogonal to a conveying direction).
In this case, conditions for generating the traveling-wave electric field are not met in areas where the wiring patterns are provided, because the areas are located outside of the electrodes. Thus, when the developer enters these areas, scattering and sticking of the developer may occur.
Incidentally, in the developing device using the traveling-wave electric field, the developer is conveyed in a predetermined direction on the developer conveying member. In this case, when the developer is conveyed in an opposite direction (counter direction) to a moving direction of the image carrying body which moves an electrostatic latent image in a circumferential direction, the moving speed of the developer in a developing area that faces the image carrying body becomes relatively fast with respect to the moving speed of the image carrying body.
This increases a collision energy for landing the developer on the image carrying body. Thus, when the developer lands at a portion on the image carrying body where the developer has already existed, the scattering of the developer may occur, thereby causing an adverse effect on the image.
Further, in the developing device as described above, the applied voltage applied to the respective electrodes is increased for increasing an amount of the developer conveyed on the developer conveying member and for reducing the occurrence of the sticking of the developer.
In this case, when the developer is conveyed in the counter direction with respect to the moving direction of the image carrying body, the increase of the applied voltage to the respective electrodes increases a speed of conveying the developer, so as to further relatively increase the moving speed of the developer in the developing area with respect to the moving speed of the image carrying body. This makes it further difficult for the developer to land on the image carrying body, so as to frequently cause the scattering, thereby causing an adverse effect on the image.
In view of the foregoing problem, the object of the present invention is to provide a developing device capable of preventing the developer from entering the wiring pattern areas outside of the electrodes on the developer conveying member, and capable of surely preventing the scattering and the sticking of the developer in the areas, and an image forming apparatus adapting the same.
In view of the foregoing problem, the object of the present invention is to provide a developing device capable of landing the developer softly on the image carrying body without scattering so as to form a stable image, and an image forming apparatus adapting the same.